Photographic emulsion and process of making same



Patented May 15, 1945 2,378,005 PHOTOGRAPH) EMULSION AND PROCESS OF MARIN Rowland 8.

Potter, Brightiord Heights, and Robert F. Brown. Rochester, N. Y., assi fender Photo Supply 00., Inc., Rochester, N.

SAME

gnora to Dea corporation of New York No Drawing. Application April 10,1949

. Serial No. 482,604

'6 Claims.

This invention relates to a photographic emulsion and process of making the same, and has for its purpose to produce a silver halide gelatin emulsion that can be made into a photographic layer having greater flexibility than when made from emulsions as heretofore produced, and as to which the finished image, or the layer after exposure and processing, is characterized by less brittleness than layers made from emulsions according to old methods.

In a more particular aspect, the invention has for its object to provide a photographic emulsion with a plasticizing agent that is insoluble in water or photographic processing solutions and which does not aiiect the photographic quality of the emulsion or the appearance of the finished image.

Various materials such as glycerine, starch syrup, and sulfonated castor oil have been used in photographic emulsions to prevent excessive brittleness of the layers upon drying, and while these materials are partially effective in causing flexibility of the layer prior to the photographic processing operations, they are water-soluble and therefore have no eflect on the brittleness of the finished image or the layer after processing. Some water-insoluble materials of a waxy nature such as the metal salts of sulfonated castor oil have been used for retaining flexibility of the layer after processing and do not wash out dur- 1 ing the processing operations, but these materials impart a dull matte-like lustre or greasy appearance to the surface of the layer or image and are therefore seriously objectionable.

It is a further purpose of the invention to afford an mulsion from which can be produced a photographic layer not open to any of the above stated objections, which has greater flexibility before and less brittleness after processing the layer, and in which the flexibility factor before processing is substantially constant and not subject to variations under changing atmospheric conditions.

Still another object of the invention is to produce photographic layers of greater flexibility than heretofore b an improved method which includes incorporating in the emulsion a colloidal dispersion of material that is insoluble in water and photographic processing solutions, that is e"si1y dispersed in water by means of a suitable dispersing agent. and that when undispersed has the character of a soft, gel-like solid at normal room temperature. Such colloidal water dispersionmust be compatible with the gelatin solutions used in the production of light-sensitive silver halide emulsions, is preferabl stable over a pH range from four to eight, and must, not affect the photographic quality of the emulsion or the appearance of the finished image or layer.

The flexibility of such a photographic layer before processing can be increased and the brittleness of the layer after processing reduced by the utilization of such water-insoluble gel-like solid in a colloidal dispersion which is incorporated in the emulsion at any stage of its production, although it has been ascertained that excellent results are had by adding the colloidal dispersion to the molten emulsion as one of the final additions immediately prior to coating on the support.

It has also been discovered that the best results are attained, giving maximum flexibility without a matted appearance in the dried emulsion layer, by having the particle size of the colloidal dispersion approach the magnitude of the micelle structure of the binding agent for the emulsion, and thus act as an internal plasticizer which increases the flexibility of the coated light-sensitive layer when dried.

Such a colloidal dispersion may be incorporated in a gelatin emulsion in an amount of the undispersed gel-like material of from five to one hundred per cent by weight oi the gelatin or other silver halide ibinding agent in the emulsion.

The invention may be carried out in various ways and is illustrated by the following examples:

Example I To 1 liter of a silver halide emulsion containing 100 grams of gelatin there is added, preferably just prior to-coating on the support, or at some other stage of its manufacture,,50 cc. of a colloidal water dispersion of the ethyl ester of acrylic acid polymerized to a state when undispersed of a soft gel-like solid at normal room temperature.

Such a dispersion may be formed by dispersing the ester in monomeric form in water with a dispersing agent such for instance as one from.

the class consisting of quaternary ammonium compounds, or one from the class consisting of sulfonated aliphatic alcohols, and a catalyst such as hydrogen or benzyl peroxide, and heating with agitation under a reflux condenser until polymerization is completed.

. The particle size of the colloidal dispersion may be further reduced by homogenizing the water dispersion of the monomeric ester before adding the catalyst.

Example I] To 1 liter of silver halide gelatin emulsion there is added, preferably just prior to coating on the support, or at an earlier stage in its manufacture, 50 cc. of a 50% colloidal water dispersion of polyvinyl acetate which has been polymerized to a state when undispersed of a soft gel like solid at normal room temperature. The colloidal dispersion may be formed and polymerization effected in substantially the same manner as in Example I.

Example III To 1 liter of a silver halide emulsion containing 100 grams of gelatin there is added, preferably just prior to coating, or at an earlier stage in its manufacture, 100 ml. of a 10% colloidal water dispersion of a gel-like material formed by mixing 33 grams of ethyl cellulose with 66 grams of diethylene glycol oleate, heating the mixture to a temperature of from 120 C. to 150 C., and cooling.

The colloidal water dispersion can be formed by dissolving the gel-like material formed as described in 100 ml. of butyl acetate, warming to approximately 75 C., and adding during rapid agitation 800 ml. of water containing a dispersing agent such as sulfonated oleyl alcohol in an amount of .5% to 1% of the total weight of material being dispersed. The size of the dispersed particles can be still further reduced by homoenization in a colloid mill.

While the invention has been described with reference to certain specific examples and procedure, it is not confined to the precise embodiments herein set forth, and this application is intended to cover such modifications, departures, or other materials or processes as may come within the purposes of the invention and the scope of the following claims.

We claim:

1. The process of flexibilizing a light-sensitive silver halide gelatin emulsion photographic layer which includes first making a water dispersion of the monomer of a water-insoluble synthetic resin selected from the group consisting of ethyl acrylate and vinyl acetate, thereafter polymerizing the resin until it is in the form of a soft gel-like solid at normal room temperature, and incorporating a colloidal dispersion of said soft gel-like solid material in the emulsion in an amount of soft gel-like solid material constituting 5% to 100% by weight of the gelatin in the emulsion to impart flexibility to the layer.

2. The process of flexibilizing a light-sensitive silver halide gelatin emulsion photographic layer which includes first making a water dispersion of monomeric acrylic acid ethyl ester, thereafter polymerizing the ethyl acrylate until it is in the form of a soft gel-like solid at normal room temperature, and incorporating a colloidal dispersion of said soft gel-like solid material in the emulsion in an amount of soft gellike solid material constituting 5% to 100% by weight of the gelatin in the emulsion to impart flexibility to the layer.

3. The process of flexibilizing a light-sensitive silver halide gelatin emulsion photographic layer which includes first making a water dispersion ofv monomeric vinyl acetate, thereafter polymerizing the vinyl acetate until it is in the form of a soft gel-like solid at normal room temperature, and incorporating a colloidal dispersion of said soft gel-like solid material in the emulsion in an amount of soft gel-like solid material constituting 5% to 100% by weight of thegelatin in the emulsion to impart flexibility to the layer.

4. A light-sensitive silver halide gelatin emulsion photographic layer containing a colloidal dispersion of a water-insoluble synthetic resin in the form of a soft gel-like solid at normal room temperature. said resin being selected from the group consisting of ethyl acrylate and vinyl acetate and polymerized while dispersed in liquid form in water, the said soft gel-like solid material constituting 5% to 100% by weight of the gelatin in the emulsion and acting to impart flexibility to the layer.

' 5. A light-sensitive silver halide gelatin emulsion photographic layer containing a colloidal dispersion of ethyl acrylate in the form of a soft gel-like solid at normal room temperature, said ethyl acrylate being polymerized while dispersed in liquid form in water and the said soft gel-like solid material constituting 5% to 100% by weight of the gelatin in the emulsion and acting to impart flexibility to the layer.

6. A light-sensitive silver halide gelatin emulsion photographic layer containing a colloidal dispersion of polyvinyl acetate in the form of a soft gel-like solid at normal room temperature, said polyvinyl acetate being polymerized while dispersed in liquid form in water and the said soft gel-like solid material constituting 5% to 100% by weight of the gelatin in the emulsion and acting to impart flexibility to the layer.

ROWLAND S. POTTER. ROBERT F. BROWN. 

